#ctci

PathBetweenNodes.java

// we can use BFS to check if there is a path between two nodes.
// Assume that we have a Node class as follows:
// public class Node{
//     boolean isVisited = false;
//     ArrayList<Node> neighbors = new ArrayList<Node>();
// }
// if the Node class does not have a boolean attribute to indicate whether it has been visited or not,
// we can always create a wrapper class that wrap a Node and a boolean variable
import java.util.Queue;
import java.util.LinkedList;
public class PathBetweenNodes{
    public boolean hasPath(Node n1, Node n2){
        if(n1 == null || n2 == null) return false;
        
        Queue<Node> queue = new LinkedList<Node>();
        queue.offer(n1);
        n1.isVisited = true;
        
        Node current = null;
        while(!queue.isEmpty()){
            current = queue.poll();
            if(current == n2) return true;
            for(Node neighbor: n1.neighbors){
                if(!neighbor.isVisited){
                    queue.offer(neighbor);
                    neighbor.isVisited = true;
                }
            }
        }
        return false;
    }    
}

line 23: "n1.neighbors" should be "current.neighbors"